In the modern electronic device industry, products are requested to have small size as well as high computation efficiency and large data storage. However, heat dissipation is required more and thus the rotation of the cooling fan must be higher when the computation efficiency is higher. As a result, structure vibration and noise are thus hard to avoid. Moreover, the data storage density of a hard drive is raised when amount of the data storage is raised, requiring more accuracy of the control of the disk and the control of reading head in the hard disk.
In view of a server, vibration and noise caused by a fan rotating at high speed may affect the hard drive's data accessing, reducing the accessing efficiency of the hard drive, and even failing the data accessing. Therefore, a thorough understanding on vibration enduring ability of a hard drive and fan vibration reducing are really important for products like servers. Except for server industry, this problem is also bothersome to any electronic device having a fan.
Fan is one of the main vibration sources in a server, so the vibration issue of the server can be solved by reducing the vibration of a fan. However, excessive variation of rotation speed will affect heat dissipation ability of the fan. It is difficult to reduce fan vibration without changing the heat dissipation ability of the fan. As a feasible way, it is possible to lower the peak value of certain frequency or to shift the frequency of a peak by modifying the structure of the fan or the like.
In the past, diagram of relation between frequency and transmission rate is utilized for confirming which frequency band is the key factor affecting the transmission rate. However, the vibration magnitude should also be taken into consideration. In the traditional measurement, the input vibration may be too intense or too weak. The relation between the frequency and the transmission rate does not contain sufficient information when the input vibration is too weak. On the contrary, the relation between the frequency and the transmission rate is meaningless as well when the input vibration is too intense, and the hard drive may even be damaged by the strong vibration. Furthermore, high frequency vibration fades quickly in structure vibration. As a result, it is difficult to find a reasonable and discriminating vibration causing examination frequency.
Generally speaking, the hard drive and the fan are fixed at the case of an electronic device. Thus, the structure vibration generated from the rotation of the fan conveys to the hard drive through the case though the fan does not contact the hard drive directly. On the other hand, the sound is generated when the fan rotates. The sound may induce air-borne vibration on the hard drive through the air. The current measurement equipment merely focuses on the structure vibration but is unable to measure the air born vibration and effect caused thereby.